The presenter hosted his entire breakfast show from the back of a bike mounted in a perspex box, and then continued to pop up during further Radio 1 shows throughout the day, as he became every more tired.

The exhausted presenter - who had been joined by stars such as Victoria Pendleton and EastEnders star Danny Dyer - slumped to the floor after finishing his all-day session at 7pm.

Within hours of embarking on the challenge he had to slip on extra padding after suffering discomfort, returning after a brief refuelling break wearing two pairs of tight cycling shorts.

"My bottom is more comfortable - but the front, less," he told listeners.

Grimshaw - who briefly ran with Davina McCall during her 500-mile Sport Relief journey last month - admitted he was not a regular cyclist.

"I don't think I've been on a bike since I was 13 - and my dad said you should be back on it because it was the only time in your life that you were thin," he admitted on air.

Grimshaw spent from 7am to 7pm on the static bike which had been positioned outside New Broadcasting House in central London.

The exertion took its toll shortly after he had started, with feelings of nausea and a loss of appetite.

"I feel like I've got a hangover," he said.

Shortly before he finished the challenge he told fans of his discomfort as he told them on Twitter: "Aaarghhhh my arse."